GPS World, September 2013

EXPERT ADVICE Looking Back to the Early Days of GPS Len Jacobson B esides my family and friends two major influences have guided my life One is GPS and the other is flying although Im not a pilot Most of the flying was on business trips for GPS Ive been writing a book about my experiences and how I helped in a small way to bring GPS to the world I estimate Ive spent about eight months aboard airplanes logging almost 25 million miles During that time I visited many places throughout the world acting as a catalyst to promote the use of GPS and to obtain GPS business for my employers and for myself I kept an extensive log of my travels and it enabled me to recreate much of what happened and my impressions of why events occurred In 1968 after two engineering degrees and five years working in communications systems I met a business development director from Magnavox which had teamed with Hughes Aircraft where I worked on a study contract We both attended a briefing on the contract status that day was my first encounter with what would become known as GPS I attended one more meeting about the 621B satellite program The U S Air Force had no funding for a full up 621B so instead it focused on proving that the technology was viable We were asked to bid on supplying a receiver that would precisely measure a half mile of cable using a spreadspectrum signal I vividly recall a Hughes VP stating that 621B would never go anywhere and besides Hughes was only interested in building synchronous satellites Our 621B competitor TRW agreed take the follow on contract TRW was acquired by Northrop Grumman in 2002 The Air Force felt it needed two competitors in case one failed so it offered a second contract to Magnavox The company took the contract which became its first hardware entry in the world of GPS Before long I received an offer from Magnavox to join the worlds leading experts on implementing anti jam communications systems using then classified directsequence spread spectrum technology Magnavox had been working in the field since it was formed in the early 1960s building the first anti jam modems for the Initial Defense Communications Satellite Program IDCSP and now pursuing a follow on program Its main business areas were satcom tactical communications and positioning programs such as the 621B receiver There also was a group building Transit satellite receivers for the Navy Transit was really the first navigation satellite growing out of experiments at Johns Hopkins University Applied Physics Lab using Sputnik signals to determine ones position on Earth by tracking the Doppler signal of a satellite in a known orbit Besides the Naval Research Lab Magnavox built the only Timation receivers an early competitor to GPS for solving military positioning needs using a satellite system A contract for a small number of initial satellites would lead to many years and billions of dollars in future GPS satellites While I was still working at Magnavox on satcom the 621B receiver was completed and we proved you could use a spread spectrum signal to accurately measure distance Once again the Air Force did not have funds to launch navigation satellites so it proceeded with a new effort called 621B User Equipment Definition and Experiments Program The prime contractor was Grumman Aircraft The idea was to put four transmitters on the ground and have an aircraft with a receiver fly over them and try to determine the aircrafts position The signals were to look as if they came from four satellites and were received by an antenna on the bottom of the plane Grumman decided to use a receiver built by Hazeltine which had some experience in spread spectrum but nowhere near as much as Magnavox For this reason the Air Force leased another receiver from us asking how much We came up with the number 450000 our development and build cost They agreed and we called the receiver the MX450 It flew beside the Hazeltine receiver on the NC 135 aircraft at the White Sands Missile Range Most of the usable test data came from the MX450 showing residual errors between the aircraft solution and the range tracking system to be less than five feet This data was crucial in getting DoD approval in 1973 to proceed with Phase 1 of GPS But we should have called it the MX495 because we overran the cost by 45000 A Tale of Two Contracts The procurement for Phase 1 GPS came together as two major contracts There would be a small number of satellites that Rockwell would win competitively and would lead to many years and billions of dollars in future GPS satellites as it became part of Boeing Corp ITT would build its own payload and go on to be the major supplier of GPS payloads to this day The other contract a study contract was awarded to three companies General Dynamics Electronics GDE Philco Ford and Grumman Two of the contractors performing that study which ended in proposals for the design of the ground network and several types of user equipment GPS receivers GPS World September 2013 www gpsworld com 8

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